Methods and apparatus for arthroscopic prosthetic knee replacement

ABSTRACT

Methods and apparatus for prosthetic knee replacement permit preparation of tibial plateau and femoral condyle surfaces and implant of tibial and femoral protheses components with the use of arthroscopic surgical techniques. The bone surfaces are resected by moving a rotating milling cutter longitudinally across the bone surface and moving the rotating milling cutter substantially laterally across the bone. Cement is supplied between the prostheses and the bone surfaces after positioning of the prostheses on the bone, and cement bonding is enhanced by applying suction to the bone to draw the cement into the bone. The apparatus for resecting the bone surfaces includes a rotating milling cutter having a body with cutting edges and holes extending through the body communicating with the interior of the body. Suction is applied to the end of the body to draw out tissue fragments through the holes and out of the body.

This is a divisional application of application Ser. No. 07/462,529filed Jan. 8, 1990.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention pertains to resection of bones for receivingprosthetic components of particular use in knee replacement proceduresand, more specifically, to methods and apparatus for arthroscopic kneereplacement.

2. Discussion of the Prior Art:

Prosthetic replacement of the knee is a procedure of substantialimportance to recreate the knee joint with a pain-free functional arc ofmotion and antero-posterior and varus-valgus stability. The knee is,basically, formed of medial and lateral tibial plateaus, medial andlateral femoral condyles and menisci between the tibial plateaus and thefemoral condyles along with the patella which covers the anteriorsurface of the knee, and prosthetic replacement of the knee as describedherein relates to the tibial plateaus, the femoral condyles and themenisci. Various types of prostheses are presently available, asdescribed in detail in Replacement of the Knee, Laskin, Denham andApley, Springer-Verlag Berlin Heidelberg, 1984, and are commonly groupedas partial or unicompartmental replacements of the medial or lateralportion of the tibio-femoral joint, surface replacements to preventcontact between worn surfaces and jack the joint surfaces apart, linkedjoints and fixed hinge joints. The type of prothesis employed must bematched to the needs of the patient. By selecting the proper prothesis,antero-posterior and varus-valgus stability can be achieved byprosthetic replacement coupled with bone surfacing or resection. In thepast, prosthetic replacement has been a last resort in treatment forknee problems due to the facts that prior art protheses and surgicalprocedures have not led to reliable, close to natural, results and theopen surgery required results in great trauma and substantial recoverytime. Much effort has been expended in attempts to improve the accuracywith which articular joint surfaces can be positioned with legalignment; however, procedures and apparatus available at this time donot provide the required accuracy to restore normal leg alignment andprevent early failure of the prothesis.

Open surgery required for prior art prosthetic replacements typicallynecessitates a long incision, on the order of ten inches, along theanterior midline of the knee from above the patella to below the tibialtubercle followed by a deep dissection around the medial border of thepatella and along the patellar ligament to the tibial tubercle withdetachment of the medial third of the quadriceps attachment from theupper border of the patella. The tendinous margin is then pulleddownwards and medially while the patella is pulled downwards andlaterally. The quadriceps tendon is then split, and the patella isdisplaced laterally and everted. While the above is a simplifiedexplanation of open knee surgery, it serves to explain the substantialtrauma and recovery time associated therewith. Arthroscopic surgery hasbeen used for many surgical procedures on the knee to avoid open surgerywith great success; however, the obstacles presented by articular bonesurface resecting or shaping to receive an implant coupled with the needfor precise positioning and alignment of the prostheses has beeninsurmountable with arthroscopic procedures prior to the presentinvention. Not only is there a great need for an arthroscopic prostheticknee replacement procedure but there is also a great need forimprovement in the accuracy of prosthesis placement to restore normalleg alignment.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to overcomethe above mentioned disadvantages associated with prior art prostheticknee replacement surgical procedures with an arthroscopic prostheticknee replacement.

Another object of the present invention is to accurately resect tibialplateau and femoral condyle planar surfaces relative to each other suchthat the tibial plateau and femoral condyle surfaces are constrained tobe disposed in planes perpendicular to a substantially verticalreference plane.

A further object of the present invention is to cement a prosthesis to atissue surface after the prosthesis is accurately placed on the tissuesurface.

An additional object of the present invention is to perform a leastinvasive prosthetic knee replacement with the use of arthroscopy andrequiring only arthroscopic size portals.

The present invention has another object in the performing of allprocedures for a prosthetic knee replacement, including surfacepreparation, fitting and implanting, arthroscopically through smallportals enlarged only for insertion of the final components.

Yet an additional object of the present invention is to arthroscopicallyresect tibial plateau an femoral condyle surfaces using existing surfaceanatomy as a reference point.

A further object of the present invention is to improve the mechanicalbond created by cement between a prosthesis and a bone surface byapplying suction to the bone to draw the cement into the bone.

Some of the advantages of the present invention over prior artprosthetic knee replacements are that, by using arthroscopic surgicaltechniques and small portals in place of the long incisions required foropen knee procedures, trauma and recovery time are substantiallyreduced, alignment of the tibial and femoral prosthesis components isassured by fixing the femoral cutting jig with reference to the tibialcutting jig and, therefore, resecting the femoral condyle with referenceto the resected tibial plateau, the knee is restored to a normal,healthy condition by resecting the tibial plateau and the tibial condyleusing the existing surface anatomy as a reference point, and prosthesesare cemented after accurate positioning of the prostheses on the bone.

Generally, the present invention contemplates the use of a millingcutter to prepare a bone surface to receive a prosthesis such that bonesurfaces can be resected through small portals allowing prosthesisimplantation using arthroscopic surgical techniques and, moreparticularly, allowing arthroscopic, unicompartmental, prosthetic totalknee replacement. Tibial and femoral prosthesis components are bonded tothe bone surfaces by injecting cement after the components areaccurately positioned on the bone, the cement being injected through thecomponents to be received in chambers defined by recesses in thefixation surfaces of the components and the cement bond being enhancedby applying suction to the bone to draw the cement into the bone.

Other objects and advantages of the present invention will becomeapparent from the following description of the preferred embodimenttaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a tibial jig mounted to the tibia inaccordance with the present invention.

FIG. 2 is an exploded view of the tibial jig, a support assembly and amilling cutter module in accordance with the present invention.

FIG. 3 is a side view of the apparatus of FIG. 2 in position forresecting the tibial plateau.

FIG. 3a is a view taken along lines 3a--3a of FIG. 3 showing a depth ofgauge scale.

FIG. 4 is a front view of the tibial plateau during the resectingthereof.

FIG. 5 is a top view of the tibial plateau after longitudinal cuts aremade therein.

FIG. 6 is a side view of the tibial plateau after resecting to produce aplanar tibial plateau surface.

FIG. 7 is a plan view of the milling cutter module mounted on a supportplatform.

FIG. 7a is a section taken along lines 7A--7A of FIG. 7 showing a stopfor limiting pivotal movement of the milling cutter.

FIG. 8 is a side view, partly in section, of the milling cutter moduleon a slide member of the platform.

FIG. 9 is a broken plan view of the milling cutter according to thepresent invention.

FIG. 10 is a section taken along lines 10--10 of FIG. 9.

FIG. 10a is a distal end view of the milling cutter of FIG. 9.

FIG. 11 is a side view of the cutter platform with an alignment bridgemounted thereon for drilling holes in the femur.

FIG. 12 is a perspective view of the alignment bridge.

FIG. 13 is a top view taken along line 13--13 of FIG. 11.

FIG. 14 is a top view showing rods passing through the holes drilled inthe femur for attachment of a femoral jig.

FIG. 15 is a broken side view partly in section of a rod for passingthrough the femur.

FIG. 16 is an exploded broken view, partly in section, of sleevesreceived on the rods.

FIG. 17 is an exploded perspective view of a femoral support base.

FIG. 18 is a top plan view of the femoral support base.

FIG. 19 is a broken side view of the femoral jig with the cutterplatform and the cutter module mounted thereon.

FIGS. 20, 21 and 22 are perspective views showing resecting of a femoralcondyle to produce planar posterior, distal and chamfer surfaces,respectively.

FIG. 23 is a broken section of a holding detent for the tibial jig.

FIG. 24 is an exploded view illustrating the prepared tibial plateau andfemoral condyle surfaces and positioning of the tibial and femoralprothesis components thereon.

FIG. 25 is a side view of a stylus for use in resecting the tibialplateau and the femoral condyle.

FIG. 26 is a perspective view of a module for the stylus mounted on theplatform slide member.

FIGS. 27, 28 and 29 are perspective views showing use of the stylus forpositioning the cutter platform for resecting the tibial plateau and thefemoral condyle.

FIG. 30 is a broken perspective view showing use of a gauge forselecting the size of a femoral prosthesis component.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The apparatus and method for prosthetic knee replacement in accordancewith the present invention requires only small portals to perform allbone and tissue preparation procedures as well as implanting theprosthetic tibial and femoral components and cementing the components inplace. Accordingly, prosthetic knee replacement in accordance with thepresent invention can be performed with the use of arthroscopic surgicalprocedures. By "portal" is meant a puncture or stab wound of the typemade by a plunge cut with a scalpel or trocar and of the type commonlyused in conventional arthoscopic procedures, the size of the portalbeing just large enough to allow insertion of instruments.

A tibial jig 40 in accordance with the present invention is illustratedin FIG. 1 and includes a lower V-block 42 adapted to rest just above themalleoli at the ankle and an upper V-block 44 adapted to be secured tothe tibia just below the tibial tubercle. Lower V-block 42 is connectedto a rod 46 telescopingly received within a tube 48 connected to upperV-block 44 which is formed of a pair of angled members having aplurality of holes 50 therein to receive screws 52 extendingtherethrough and into the tibia to securely mount the tibial jigthereon. As best shown in FIG. 2, tube 48 has spaced arms 54 and 56terminating at the angled members of upper V-block 44, and an angularadjustment member 58 has a tongue 60 disposed between members 54 and 56with a hole 62 therein for receiving an adjustment screw 64 extendingthrough corresponding holes in members 54 and 56. In this manner, theangular adjustment member 58 can be pivoted about screw 64 to a desiredposition and the screw tightened to hold the angular adjustment memberin place. A longitudinal adjustment block 66 has a dovetail slot 68therein to receive a dovetail 70 on member 58, and a longitudinaladjustment screw 72 is held in a non-rotating manner in block 66 andcarries a head 74 having a dovetail slot 76 therein. Block 66 has spacedarms between which is mounted a thumbwheel 76 threadedly engagingadjustment screw 72 such that rotation of thumbwheel 76 causeslongitudinal axial movement of the screw and the head. A block 80 has adovetail 82 received in slot 76 and mounts a cutter platform generallyindicated at 84. As shown in FIGS. 3 and 3a, a longitudinal or depth ofcut gauge 86 is mounted on an extension 88 of block 66 and carriesindicia 90 allowing registration with an index mark on screw 72 toindicate the depth of a cut being made, as will be explained in moredetail hereinafter. The gauge has a zero center mark with indiciaextending in either direction therefrom in millimeter graduations.

The platform 84 includes a semi-circular plate 92 having a curvedperipheral edge 94 and a dovetail 96 slidably received in a dovetailslot 98 in block 80 to permit movement of the platform in a lateraldirection perpendicular to the longitudinal movement of screw 72. Alinear slide member 100 has a distal end 102 pivotally mounted centrallyon plate 92 and carries a toothed rack 104 longitudinally thereon. Theslide member 100 extends substantially beyond the peripheral edge 94 ofplate 92 and carries on its back side a clamp assembly including a lever106 pivotally mounted on ears 108 secured to the slide member, the lever106 having a clamping end 110 and an operating end 112 as best shown inFIG. 8. A trigger like member 114 is pivotally mounted on a lug 116extending from the slide member and has a flat portion engaging theoperating end 112 of lever 106 which is biased against the trigger bymeans of a compression spring 118. Accordingly, when trigger 114 ismoved toward the slide member (rotated clock-wise looking at FIG. 8) theoperating end 112 of lever 106 is moved toward the slide member causingthe clamping end 110 to move away from the peripheral edge 94 of plate92 thereby allowing pivotal movement of the slide member relative to theplate. When the trigger 114 is released, the spring 118 returns theclamping end 110 to engagement with the plate to hold the slide memberin the selected pivotal position.

The slide member has an elongated dovetail 121 received in a slot 122 ina housing 124 of a cutter module generally indicated at 126. A pinion128 having teeth for engaging rack 104 is mounted on an axle journaledthrough housing 124 to terminate at handwheels 132 on either side of thehousing. A pneumatic motor 134 has a proximal end receiving drive andexhaust conduits 136 and a distal end engaging the shaft of a millingcutter 138 as best shown in FIG. 8. The motor is driven by pressurizedfluid, such as nitrogen or air; and, when the drive fluid is provided at100 psi, the motor speed and torque are 4000 rpm and 50 oz-inch,respectively. A chamber 140 is formed around the drive coupling and hasa port 142 for connection to a source of suction, the proximal end ofthe milling cutter 138 having a hole 144 therein for communicating withthe chamber and the milling cutter 138 being rotatably supported at thedistal end of the chamber by suitable bearing and journal structure.Stops 146 and 148 are movably secured to the peripheral edge 94 of plate92 on opposite sides of slide member 100; and, as shown in FIG. 7a, areformed of set screws 150 for engaging the plate 92.

The milling cutter 138, as best shown in FIGS. 9, 10 and 10a, includes ashaft having a proximal end 152 for engaging a locking collet assemblyin chamber 140 to be driven by the pneumatic motor, the shaft beinghollow to establish communication between hole 144 in the proximal endthereof and holes 154 disposed in the distal portion thereof. The distalportion of the milling cutter includes a body 156 having a plurality ofhelical cutting edges 158 extending therealong, and at least one hole154 is disposed between each pair of body cutting edges 158. As shown inFIG. 10, four equally spaced cutting edges are disposed on the flutedbody 156, and holes 154 communicate with a passage 160 formed by thehollow shaft of the milling cutter. Cutting edges 162 are disposed atthe distal end of the milling cutter in a plane extending transverse tothe longitudinal axis of the milling cutter, and each of the bodycutting edges 158 extends from one of the distal end cutting edges 162.The milling cutter preferably has a diameter of 7 mm and the bodycutting edges preferably have substantially radial leading edges.

The operation of the apparatus described above to resect a tibialplateau for unicompartmental prosthetic knee replacement utilizingarthroscopic surgical techniques will be described with reference toFIGS. 1 and 3. As previously described, tibial jig 40 is secured to thetibia by screws 52 extending through V-block 44 and into the tibia withthe upper and lower V-blocks disposed just below the tibial tubercle andjust above the malleoli at the ankle, respectively, with a set screw 163provided to maintain the position of telescoping members 46 and 48. Aportal 164 is formed in the knee for insertion of an arthroscope 166 forviewing of the knee and the surgical procedure, while a portal 168 isformed in the tissue adjacent the tibial plateau, FIG. 1 illustratingthe portal 168 for use in resecting the medial tibial plateau of theleft leg. With the tibial jig 40 secured in alignment with the tibia,the apparatus is assembled as illustrated in FIG. 3 with the exceptionthat the cutter module is not mounted on the slide member 100 but rathera stylus module 170, as illustrated in FIG. 26, is mounted thereon. Thestylus module 170 includes a housing having a dovetail slot forreceiving the dovetail 120 of the slide member and mounts a stylus 172having four equally spaced positions controlled by detents, not shown,within the housing. The stylus has a curved radially extending tip 174that can be positioned via the detents to extend up, down or to eitherside. The radial extension of the stylus 174 is preferably equal to theradius of the milling cutter, e.g., 3.5 mm, and the housing of thestylus module positions the stylus at the same position at which themilling cutter is positioned when the cutter module is received on theslide member. With the stylus tip turned down, the posterior andanterior edges of the tibial plateau are contacted with the stylus, andangular adjustment block 58 is pivoted about screw 64 to align theplatform with the natural tilt of the tibial plateau as sensed by thestylus, the natural tilt being normally between 3° and 10° posteriorly.Once the natural tilt is established, the stylus is rotated 90° suchthat the tip 174 is turned to the right, and the tip of the stylus ismoved by sliding the plate 92 in block 80 until the tip of the styluscontacts the tibial eminence 176 as illustrated in FIG. 27. Once thetibial eminence has been located, a screw, not shown, is tightened tosecure the lateral position of the platform. The slide member 100 iscentrally positioned on the plate 92 during this procedure, and the stop148 is moved to abut the slide member 100 to prevent pivotal movement ofthe slide member and the milling cutter mill clockwise looking at FIG.7. With the tip 174 of the stylus turned down, the lowest point ofcontact of the tip on the tibial plateau is located; and, with thestylus at this contact point, thumbwheel 78 is locked in place tocontrol the position of the resection to be performed, it being notedthat, due to the dimensional relationship between the cutter module andthe stylus module, the milling cutter will be aligned with the lowestpoint on the tibial plateau. As shown in dashed lines in FIG. 27, priorto the alignment steps, the anterior portion of the meniscus orcartilage has been removed by normal arthroscopic techniques leaving aposterior segment indicated at 178 such that during the resectionprocedure, the posterior portion of the meniscus provides a cushion toprovide the surgeon with an indication of the location of the posterioredge of the tibial plateau.

To resect the tibial plateau, the stylus module is removed and thecutter module is placed thereon as illustrated in FIG. 3; and, sinceangular, lateral and longitudinal adjustments have already been made andset in place, only linear and pivotal movements of the milling cuttercan be made and such movements can be made only in a single plane. Withreference to FIGS. 4 and 5, it can be seen that initial forward movementof the milling cutter produces a longitudinal plunge cut along thetibial eminence 176 to produce a trough across the tibial plateau asindicated at 180, it being noted that the milling cutter cuts on itsdistal end as well as along the fluted body thereof. After the firstlongitudinal cut has been made, the trigger 114 is released allowingpivotal movement of the slide member slightly; and, after the trigger isreleased to clamp the slide member in position, a second longitudinalcut is made by linear movement of the milling cutter as indicated at182. This procedure is repeated until the surface of the tibial plateauis covered with troughs having ridges 184 therebetween. The trigger 114is now depressed to release the slide member; and, with the millingcutter disposed over the tibial plateau, the milling cutter is pivotedback and forth to sweep the milling cutter over the tibial plateauremoving the ridges, the sweeping movement being substantiallytransverse to the longitudinal movements of the milling cutter to formthe troughs. During the resecting procedure, suction is applied to port142 such that bone chips are evacuated via holes 154 and passage 160through the hollow milling cutter. The suction also serves to cool thesurgical site and prevent cavitation.

Once the tibial plateau has been resected, the cutter module is removedfrom the platform, and the platform is removed from block 80. Analignment bridge 186, as illustrated in FIG. 12, is then coupled withblock 80 as illustrated in FIGS. 11 and 13, it being noted that block 80remains fixed relative to the tibia and, therefore, the resected planartibial plateau. The alignment bridge 186 includes a dovetail slide 188received in the slot 98 in block 80, and an arm 190 extends at an angleof 45° between slide 188 and a drill guide 192 having parallel bores 194and 196 therethrough. Accordingly, the bores 194 and 196 will bedisposed in a plane transverse to the plane of the resected tibialplateau. With the leg in full extension, as illustrated in FIGS. 11 and13, inserts 198 and 200 are passed through bores 194 and 196,respectively, to provide elongated guides for drilling parallel boresthrough the femur. The bores are drilled through the femur usingconventional orthopedic techniques; and, after the bores are drilledthrough the femur, threaded rods 204 are passed through each bore asillustrated in FIG. 14. As shown in FIG. 15, one of the threaded rods204 is preferably hollow having a passage 206 therethrough providingcommunication between its end and holes 208 centrally located therein.Threaded sleeves 210 are disposed on the outer ends of each rod inthreaded engagement with the rods while loosely sliding sleeves 212 aredisposed between sleeves 210 and the femur, the sleeves beingillustrated in FIG. 16 and shown in position relative to the femur inFIG. 14. With the sleeves tightened in place and the rods passingthrough the epicondylar region of the femur, a support for resecting thefemoral condyle is established relative to the resected tibial plateausince the rods are disposed in a plane perpendicular to the planartibial plateau. With the rods in place, a femoral support base 214 isrigidly attached to the rods to prevent any deflection or twisting ofthe rods. The femoral support base 214 includes a U-shaped member 216having upper ends secured saddles 218 each of which has a cylindricalprotrusion 220 extending upwardly therefrom and side walls 219 spacedfrom the cylindrical protrusion to allow the sleeves 210 to fittherebetween. Conical washers 222 are secured over the sleeves by meansof screws 224 received in threaded holes 226 in the saddles 218 suchthat the washers abut the sleeves to firmly hold the rods in parallelposition.

A femoral cutting jig 228 is mounted to the femoral support base 214 viathreaded posts 230 extending through the cylindrical protrusions 220 toreceive threaded nuts 232 tightening the femoral cutting jig in rigidposition relative to the femoral support base. The femoral cutting jigincludes a U-shaped member 234 having opposite legs pivotally mounted onflanges 236 each of which is rigidly secured to the femoral support basevia threaded post 230. As best shown in FIGS. 20, 21 and 22, each of theflanges 236 has holes 238, 240 and 242 therein positioned relative tothe pivotal axis indicated at 244 to position a support 246 rigidlyconnected with the U-shaped member 234 in a plane parallel to the planepassing through the rods through the femur as illustrated in FIG. 21, aplane perpendicular to the plane passing through the rods as illustratedin FIG. 20, and a plane positioned at an angle of 45° to the planepassing through the rods as illustrated in FIG. 22. The position of theU-shaped member and therefore the support 246 is controlled by means ofspring loaded detents mounted on flanges 248 secured to the oppositeends of the U-shaped member. As shown in FIG. 23, detents 250 are biasedinwardly to extend through holes 238, 240 or 242 with which they arealigned, and can be withdrawn by twisting end 252 to cause the end tocam outwardly as shown in phantom compressing a spring 254 to move thedetent out of the hole. Accordingly, the femoral cutting jig can beaccurately positioned in either of the three positions shown in FIGS.20, 21 and 22 by manipulating the detents and pivoting the U-shapedmember relative to the femoral support base. The femoral cutting jigillustrated in FIG. 19 differs slightly from that illustrated in FIGS.20, 21 and 22 in that the support 246 is secured at an angle to theU-shaped member 234; however, the operation is the same in thatpositioning of the femoral cutting jig only requires accuratepositioning of the support 246 to which the longitudinal adjustmentblock 66 is attached to mount the cutting platform and the cuttingmodule in a plane perpendicular to support 246 in the same manner asdescribed above with respect to mounting of the cutting platform and thecutting module on angular adjustment block 58 mounted on the tibial jig.FIG. 19 illustrates the milling cutter positioned at an angle of 45° tothe plane of the rods 204 through the femur and further illustrates, inphantom, the milling cutter positioned in planes perpendicular andparallel to the plane of the rods 204. Since the plane of the rods 204is parallel to the planar resected tibial plateau, the milling cutter isconstrained to move only in planes parallel to a reference planeextending perpendicular to the plane of the resected tibial plateau.

To resect the femoral condyle, the stylus module 170 is mounted on theslide member 100 with the stylus 172 turned upward as illustrated at 256in FIG. 29 and the slide member positioned in a plane parallel to theresected tibial plateau plane, and the stylus is moved to contact thelowermost point on the posterior surface of the femoral condyle. Oncethis point is located, the depth gauge 86 is moved to align the "zero"point with the index line on the screw 72. With the depth gauge soaligned, the stylus module is removed, and the thumbwheel 78 is rotatedto move the cutting platform 7 millimeters toward the femoral condyle asindicated by the gauge 86. With the depth of cut now set and the lateralposition set by viewing the position of the stylus via the arthroscope,the cutting module is positioned on the slide member and the posteriorportion of the femoral condyle is resected in the same manner asdescribed above with respect to the tibial plateau, that is, by forminga plurality of longitudinal troughs in the bone and removing the ridgestherebetween by sweeping the milling cutter. With reference to FIG. 20,it can be seen that resecting of the posterior surface of the femoralcondyle is accomplished by passing the milling cutter and the stylusthrough the same portal 168 utilized to resect the tibial plateau.

After resection of the posterior surface of the femoral condyle, thedistal surface of the femoral condyle is resected by moving the femoralcutting jig to position the platform in a plane perpendicular to theplane of the rods passing through the femur and the plane of theresected posterior surface of the femoral condyle. The stylus module andthe depth gauge are used in the same manner as described with respect tothe resecting of the posterior surface; however, as illustrated in FIG.21, a second portal 258 disposed between an inch and an inch and a halfabove portal 168 is utilized for the distal surface cutting procedure.As shown in FIG. 29, the stylus is turned toward the condyle asindicated at 260; and, when the resecting procedure is completed, theresected planar distal surface will be perpendicular to the resectedplanar posterior surface. Resection of the distal surface isaccomplished in the same manner as described above with respect to thetibial plateau and the posterior surface.

Once resection of the distal surface is completed, the femoral cuttingjig is pivoted to the position illustrated in FIG. 22 such that theplatform is disposed in a plane at an angle of 45° to the distal andposterior resected surfaces. The stylus is mounted on the platform andpassed through portal 258 to contact the uncut portion of the femoralcondyle between the resected posterior and distal surfaces as shown at262, and the depth gauge and cutter module are utilized in the samemanner as described above to cut a chamfer surface between the distaland posterior surfaces, the chamfer surface being disposed in a plane atan angle of 45° to the planes of the distal and posterior surfaces. Aplurality of semi-circular gauges 264, each having an anterior foot 266and a posterior foot 268, are provided; and, to determine the length ofthe chamfer cut, individual gauges are attached to a rod 270 insertedthrough portal 258 and aligned with the chamfer cut to determine thesize of the femoral prothesis for use with the contoured femoralcondyle.

FIG. 24 illustrates the medial compartment of the knee after resection,and it will be appreciated that the planes of each of the posterior,distal and chamfer cuts on the femoral condyle are parallel to areference plane perpendicular to the plane of the tibial plateau, thereference plane being substantially vertical thereby producing a normalhealthy knee joint. The resected planar tibial plateau is indicated at272, the posterior planar femoral condyle cut is indicated at 274, thedistal planar femoral condyle cut is indicated at 276 and the chamferplanar femoral condyle cut is indicated at 278. Once all of theresections have been performed as described above, the area betweenportals 168 and 258 is incised to increase the size of the portal toabout one and one-half inches as indicated at 280. The tibial jig isremoved once the rods are inserted in the femur to establish the femoralsupport base; and, once the resections are completed, the femoralsupport base and the femoral cutting jig are removed. A drill guide 282mounted on a rod 284 is inserted into the joint through portal 280, thedrill guide having a distal portion for abutting distal planar surface276 and a chamfer portion 286 for abutting chamfer surface 278, theangle between portions 286 and 288 being 45° to equal the angle betweendistal surface 276 and chamfer surface 278. With the guide 282 alignedon the prepared femoral condyle, spaced holes 290 are drilled in thedistal surface. Since the same amount of bone has been removed from eachcut during contouring of the femoral condyle, a femoral prothesiscomponent 292 can be implanted on the femoral condyle reproducing thenatural condyle. Tibial component 292 has a polycentric bearing surface294 with an inner fixation surface 296 for engaging the posterior,distal and chamfer surfaces, and spaced tapered posts 298 extend from adistal portion of the femoral component to be received in holes 290. Achannel 300 is formed in the femoral component to communicate with arecess 302 formed in the fixation surface 296 such that the femoralcomponent can be installed in proper position on the prepared femoralcondyle with the posts 298 received in the holes 290; and, thereafter,cement can be introduced between the femoral component and the bone viachannel 300, the cement filling the recess 302 and producing amechanical bond with the bone. The mechanical bond of the cement withthe bone is enhanced by applying suction to rod 204, the suction beingcommunicated via passage 206 and holes 208 and through the porous boneto draw the cement into the bone.

Prior to installation of the final tibial prothesis component, a trialtray similar in shape to tibial component 304 illustrated in FIG. 24 isplaced on tibial plateau 272 via portal 280 to obtain the correct size,and various bearing inserts similar to bearing insert 306 illustrated inFIG. 24 are positioned in cavities in the tray to provide the desiredtibial component thickness allowing alignment of the femur and tibiawith the femoral component bearing on the bearing insert. When theproper spacing is determined, a permanent tibial prothesis implant 304is passed through portal 280 and secured to tibial plateau 272. Thetibial component 304 has a cavity 308 in the upper surface thereof forreceiving bearing insert 306 in locking engagement, and, similar tofemoral component 292, a recess 310 is formed in a bottom fixationsurface 312 and a channel 314 communicates therewith for supplyingcement to the tibial component after the tibial component is placed onthe tibial plateau. A bone screw passes through an angled hole 316 in ananterior portion of the tibial prothesis 304 to hold the prothesis onthe tibial plateau. The tibial and femoral prosthesis components and thebearing insert are disclosed in an application filed concurrentlyherewith by the same inventors entitled "Knee Joint Prosthesis", thedisclosure of which is incorporated herein by reference. In practice,removable trial femoral components can be placed on the femoral condyleto assist in selection of proper tibial component thickness, and eitherthe tibial component or the femoral component can be cemented in placebefore the other.

From the above, it will be appreciated that the method and apparatus ofthe present invention permits prosthetic knee replacement utilizingarthroscopic surgical procedures. Additionally, the method and apparatusprovide advantages useful in open knee surgery also in that the cuts inaccordance with the present invention are different for each individualsince each cut is sensed from the surface and not from a previous cutthereby restoring a natural knee action in that making the cuts withreference to bone surfaces allows replication of the previous bonestructure thereby not forcing alignment and allowing the compartment tobe matched with the other compartments of the knee. Additionally, byestablishing the femoral jig in the femur in relation to the tibialplateau, alignment of the femoral and tibial protheses is assured withbearing contact along a line laterally through the knee joint. Theplatform and cutting module permit the cutting action to be performed bythe surgeon with only one hand allowing his second hand to move thearthroscope or to provide better viewing in open surgery. The resectingof bone using a pivoting movement of a cutter is particularlyadvantageous in that, by placing the pivot point just external of thebody, small portals can be used in accordance with arthroscopictechniques.

Inasmuch as the present invention is subject to many variations,modifications and changes in detail, the subject matter discussed aboveand shown in the accompanying drawings is intended to be illustrativeonly and not to be taken in a limiting sense.

What is claimed is:
 1. Apparatus for resecting bone in the body of apatient comprisinga rotatable elongate milling cutter having a bodyterminating at a distal end, a plurality of radially extending endcutting edges disposed on said distal end and a plurality of sidecutting edges extending along said milling cutter body for resectingbone externally of said milling cutter body whereby bone chips areproduced externally thereof, and an interior passage in said millingcutter body; and means on said milling cutter for evacuating bone chipsfrom externally of said milling cutter body to said interior passage forevacuation from the patient's body through said passage.
 2. Apparatusfor resecting bone as recited in claim 1 wherein said milling cutter ishollow and said evacuating means includes at least one aperture disposedin said milling cutter body and communicating with said interiorpassage.
 3. Apparatus for resecting bone as recited in claim 2 includinga plurality of said apertures with at least one of said aperturesdisposed between each pair of said side cutting edges.
 4. Apparatus forresecting bone as recited in claim 3 wherein said milling cutterincludes a longitudinal axis, said distal end cutting edges are disposedin a plane extending transverse to said longitudinal axis of saidmilling cutter and said side cutting edges each extend from one of saiddistal end cutting edges and having a helical configuration. 5.Apparatus for resecting a bone in the body comprisingmilling cuttermeans; platform means for supporting said milling cutter means formovements therealong in a cutting plane and including means forsupporting said milling cutter means for longitudinal and pivotalmovements relative to said platform means in said cutting plane; meansfor mounting said platform means relative to the bone; and longitudinaladjustment means coupled with said platform means for moving saidplatform means and said cutting plane relative to said mounting means ina direction perpendicular to said cutting plane.
 6. Apparatus forresecting bone as recited in claim 5 wherein said platform meansincludes a pivotally mounted slide member supporting said milling cuttermeans for sliding movement therealong.
 7. Apparatus for resecting boneas recited in claim 6 wherein said platform means includes stop meansfor limiting pivotal movement of said slide member.
 8. Apparatus forresecting bone as recited in claim 6 wherein said platform meansincludes a support member pivotally mounting said slide member andselectively engageable clamp means for securing said slide member at aselected angular position relative to said support member.
 9. Apparatusfor resecting a bone as recited in claim 8 wherein said slide membersupports said milling cutter means for movement in said cutting plane,said support member is movably mounted to adjust the position of saidmilling cutter means in said cutting plane, and said longitudinaladjustment means is coupled with said support member.
 10. Apparatus forresecting bone as recited in claim 9 wherein said platform meansincludes angular adjustment means coupled with said support member foradjusting the angular orientation of said cutting plane.
 11. Apparatusfor resecting a bone in the body comprisingmilling cutter means;platform means for supporting said milling cutter means for movementstherealong in a cutting plane and including means for supporting saidmilling cutter means for longitudinal and pivotal movements relative tosaid platform means in said cutting plane; and means for mounting saidplatform means relative to the bone, said mounting means including a jigfor attachment to the bone and adjustment means coupled with saidplatform means for adjusting the angular position of said platform meansrelative to said jig.
 12. Apparatus for resecting a bone in the bodycomprisingmilling cutter means; platform means for supporting saidmilling cutter means for movements therealong in a cutting plane andincluding means for supporting said milling cutter means forlongitudinal and pivotal movements relative to said platform means insaid cutting plane; and means for mounting said platform means relativeto the bone, said mounting means including a jig for attachment to thebone and adjustment means coupled with said platform means for adjustingthe longitudinal position of said platform means relative to said jig.13. Apparatus for resecting a bone in the body comprisingmilling cuttermeans; platform means for supporting said milling cutter means formovements therealong in a cutting plane and including means forsupporting said milling cutter means for longitudinal and pivotalmovements relative to said platform means in said cutting plane; andmeans for mounting said platform means relative to the bone, saidmounting means including a jig for attachment to the bone and adjustmentmeans coupled with said platform means for adjusting the lateralposition of said platform means relative to said jig.
 14. Apparatus forresecting a bone in the body comprisingmilling cutter means; platformmeans for supporting said milling cutter means for movements therealongin a cutting plane and including means for supporting said millingcutter means for longitudinal and pivotal movements relative to saidplatform means in said cutting plane; and means for mounting saidplatform means relative to the bone, said mounting means including a jigfor attachment to the bone and adjustment means coupled with saidplatform means for adjusting the longitudinal and lateral positions ofsaid platform means relative to said jig.